Power saving device and electronic device using the same

BACKGROUND OF THE INVENTION

00011. Field of the Invention

0002The present invention relates to a power saving device in which a microcomputer is shut down in a standby state.

00032. Description of the Related Art

0004An electronic device such as an AV device has a standby state, where power is supplied only to the microcomputer and to the peripheral circuits thereof so that the power of the device can be turned back ON in response to a user's operation of a remote control even when the power of the device is OFF. Recently, there is a demand for further reducing the standby power consumption, i.e., the amount of power to be consumed in a standby state. In view of such a demand, the microcomputer has a power saving mode in which the microcomputer itself is shut down when the microcomputer has no process to execute. Then, in response to a remote control signal, an interrupt signal is input to an interrupt terminal of the microcomputer for triggering a transition from the power saving mode to the normal mode. If the remote control signal is a signal that does not require the transition to the normal mode (e.g., a “Stop” signal of a CD player), the microcomputer transitions from the normal mode back to the power saving mode. However, whether the remote control signal does or does not require the transition to the normal mode can be determined only after receiving the remote control signal completely. With a conventional method, the microcomputer stays in the normal mode while analyzing the remote control signal. Therefore, such a conventional method fails to save the power consumption during the remote control signal receiving period.

0005Patent Document 1 (Japanese Laid-Open Patent Publication No. 2001-14073) discloses a device in which the microcomputer in the standby state performs an intermittent operation in which the power saving mode and the normal mode are alternated with each other until a remote control signal is received. When a remote control signal is received, the normal mode is extended (continued) to analyze the remote control signal. With this device, however, the microcomputer is in the normal mode while analyzing a remote control signal, thereby failing to save the power consumption during the remote control signal receiving period. Moreover, since this device performs the intermittent operation and repeats the normal mode at regular intervals until a remote control signal is received, thereby increasing the average power consumption. The device performs the intermittent operation until a remote control signal is received because the device aims at making the transition from the power saving mode to the normal mode by detecting the input of the remote control signal without using an interrupt terminal.

0006Patent Document 2 (Japanese Utility Model No. 3065058) discloses a device having two different modes, i.e., the normal mode and the power saving mode in which the power consumption is smaller than that in the normal mode. When making the transition from the power saving mode to the normal mode, the device alternately repeats the normal mode and the power saving mode and then transitions to a continuous normal mode. The average current consumption value during the period in which the normal mode and the power saving mode are alternately repeated is smaller than the current consumption value in the normal mode. The device can gradually increase the average power consumption by gradually increasing the period of the normal mode in the intermittent operation. With this device, the intermittent operation is performed after the remote control signal is received completely. This delays the time at which an operation specified by the remote control signal is started. Another problem is that the power consumption during the remote control signal receiving period cannot be reduced.

SUMMARY OF THE INVENTION

0007It is therefore an object of the present invention to provide a power saving device capable of desirably reducing the power consumption of a microcomputer in a standby state.

0008A device of the present invention is a power saving device operable in a power saving mode and in a normal mode, including a controller including an interrupt terminal for receiving a first interrupt signal based on an input remote control signal. When the first interrupt signal is input to the controller via the interrupt terminal, the controller performs an intermittent operation in which the power saving mode and the normal mode are periodically alternated with each other. The controller ends the intermittent operation when the remote control signal is received completely.

0009The controller periodically repeats the power saving mode and the normal mode while a remote control signal is being received. Therefore, the controller can analyze the remote control signal during the normal mode, while reducing the power consumption during the power saving mode. Thus, it is possible to desirably reduce the average power consumption during the remote control signal receiving period. The intermittent operation is ended when the remote control signal is received completely, and the operation can immediately transition to the power saving mode if the remote control signal contains no instruction that needs to be executed. Thus, it is possible to further reduce the power consumption. It is determined that a remote control signal is received completely not only when the remote control signal is received normally and completely, but it is assumed that a remote control signal is received completely also when the remote control signal is discarded for reasons such as the leader code (or the custom code) being invalid or an interference signal contaminating the remote control signal, whereby the code cannot be analyzed properly.

0010In a preferred embodiment, the controller stays in the power saving mode until the first interrupt signal is input to the controller via the interrupt terminal.

0011Therefore, the controller always stay in the power saving mode until a remote control signal is input, whereby it is possible to further reduce the standby power consumption.

0012In a preferred embodiment, if the remote control signal is a power-requesting signal, the controller stays in the normal mode after the intermittent operation, and if the remote control signal is a non-power-requesting signal, the controller stays in the power saving mode after the intermittent operation.

0013If the remote control signal is a power-requesting signal, the controller transitions to the normal mode after the intermittent operation, whereby the controller can perform an operation based on the remote control signal. If the remote control signal is a non-power-requesting signal, the controller transitions to the power saving mode after the intermittent operation, whereby it is possible to further reduce the power consumption.

0014In a preferred embodiment, the controller includes a main circuit, and a timer circuit for giving a second interrupt signal to the main circuit when the timer circuit has counted a predetermined amount of time. The intermittent operation includes: a step in which the timer circuit counts the predetermined amount of time; a step in which the controller transitions from the normal mode to the power saving mode; a step in which the timer circuit gives the second interrupt signal to the main circuit when the timer circuit has counted the predetermined amount of time; and a step in which the controller transitions from the power saving mode to the normal mode when the main circuit receives the second interrupt signal.

0015When the first interrupt signal is input to the interrupt terminal, the controller transitions to the normal mode, and the timer circuit starts the count operation. Then, the controller analyzes the remote control signal during the normal mode, after which the controller transitions to the power saving mode. The timer circuit gives the second interrupt signal to the main circuit when the timer circuit has counted the predetermined amount of time, and the controller transitions to the normal mode in response to the second interrupt signal. The controller can perform the intermittent operation because the controller can automatically transition to the power saving mode and to the normal mode in response to the second interrupt signal from the timer circuit.

0016In a preferred embodiment, the controller includes a main circuit, a timer circuit for giving a second interrupt signal to the main circuit when the timer circuit has counted a predetermined amount of time, and an oscillator circuit for supplying a clock signal to the main circuit and the timer circuit. The power saving mode until the first interrupt signal is input to the interrupt terminal is a first power saving mode in which the oscillator circuit does not supply a clock signal to the main circuit or the timer circuit. The power saving mode during the intermittent operation is a second power saving mode in which the oscillator circuit does not supply the clock signal to the main circuit but supplies the clock signal to the timer circuit.

0017Until a remote control signal is input, the controller is in the first power saving mode in which the oscillator circuit does not supply the clock signal to the main circuit or the timer circuit. This is because the timer circuit does not need to be operated. Therefore, the controller can desirably reduce the power consumption. During the intermittent operation, the controller is in the second power saving mode in which the clock signal is not supplied to the main circuit but is supplied to the timer circuit. Therefore, it is possible to desirably reduce the power consumption by not supplying the clock signal to the main circuit, while the timer circuit can perform the count operation as the clock signal is supplied to the timer circuit. Thus, it is possible to desirably reduce the average power consumption of the controller.

0018Another device of the present invention is a power saving device operable in a power saving mode and in a normal mode, including a controller including an interrupt terminal for receiving a first interrupt signal based on an input remote control signal. The controller stays in the power saving mode until the first interrupt signal is input to the controller via the interrupt terminal. When the first interrupt signal is input to the controller via the interrupt terminal, the controller performs an intermittent operation in which the power saving mode and the normal mode are periodically alternated with each other.

0019The controller stays in the power saving mode until a remote control signal is input. The controller periodically repeats the power saving mode and the normal mode while a remote control signal is being received. Therefore, the controller can analyze the remote control signal during the normal mode, while reducing the power consumption during the power saving mode. Thus, it is possible to desirably reduce the average power consumption of the controller.

BRIEF DESCRIPTION OF THE DRAWINGS

0020<figref idref="DRAWINGS">FIG. 1</figref> is a block diagram showing a power saving device according to a preferred embodiment of the present invention.

0021<figref idref="DRAWINGS">FIG. 2A</figref> and <figref idref="DRAWINGS">FIG. 2B</figref> are timing charts each showing an operation of the power saving device of the preferred embodiment.

0022<figref idref="DRAWINGS">FIG. 3</figref> is a flow chart showing an operation of the power saving device of the preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

0023While a preferred embodiment of the present invention will now be described with reference to the drawings, it is understood that the present invention is not limited thereto. <figref idref="DRAWINGS">FIG. 1</figref> is a schematic block diagram showing a power saving device <b>10</b> according to the preferred embodiment of the present invention. The power saving device <b>10</b> includes a controller <b>11</b> and a remote control signal receiving circuit <b>12</b>, and transitions from the power saving mode to the normal mode in response to a received interrupt signal. The power saving device <b>10</b> can be used in a common electronic device such as a CD player.

0024The controller <b>11</b> controls the overall operation of an electronic device (e.g., a CD player) with which the power saving device <b>10</b> can be used (i.e., it controls a controlled section <b>15</b>), and is typically a microcomputer, for example. The microcomputer <b>11</b> includes a memory <b>13</b> (e.g., a ROM and/or a RAM), which may be provided in the microcomputer <b>11</b> or may be provided outside and connected to the microcomputer <b>11</b> via a bus, or the like. The microcomputer <b>11</b> executes various programs stored in the memory <b>13</b> to perform various operations (e.g., bringing a CD player to the Play mode). The microcomputer <b>11</b> includes a main circuit <b>16</b> for controlling the controlled section <b>15</b>, an oscillator circuit <b>17</b> and a timer circuit <b>18</b>. The oscillator circuit <b>17</b> produces a clock signal, and supplies the produced clock signal to the main circuit <b>16</b> and the timer circuit <b>18</b>. The timer circuit <b>18</b> receives the clock signal from the oscillator circuit <b>17</b>, and counts a predetermined amount of time based on the clock signal. Specifically, the timer circuit <b>18</b> counts a predetermined amount of time by counting the number of pulses of the clock signal. Upon completion of the counting of a predetermined amount of time, the timer circuit <b>18</b> gives a second interrupt signal to the main circuit <b>16</b>. The second interrupt signal is used for triggering the transition to the normal mode in the intermittent operation to be described later. The main circuit <b>16</b> receives the clock signal from the oscillator circuit <b>17</b> and performs various operations. Moreover, the main circuit <b>16</b> instructs the oscillator circuit <b>17</b> to stop the supply of the clock signal, and/or instructs the timer circuit <b>18</b> to start/stop the count operation.

0025The power saving device <b>10</b> has a so-called “standby mode” in which the power is supplied only to the microcomputer <b>11</b>, the memory <b>13</b> and the remote control signal receiving circuit <b>12</b> so that the main power can be turned ON by a user's operation of the remote control. Specifically, the main power supply is electrically connected to the power saving device <b>10</b> as a whole, whereas the standby power supply is electrically connected only to the microcomputer <b>11</b>, the memory <b>13</b> and the remote control signal receiving circuit <b>12</b>. In the standby state, the main power is OFF, and only the standby power is ON. An OFF state as used herein refers to a state where the power is not being supplied as it is stopped by a switch (not shown), for example, being open, and an ON state as used herein refers to a state where the power is being supplied through the switch being closed.

0026The modes of operation of the microcomputer <b>11</b> include the normal mode and the power saving mode. The normal mode is a state where the microcomputer <b>11</b> can perform operations, and more specifically a state where a clock signal is supplied from the oscillator circuit <b>17</b> to the main circuit <b>16</b>. The power saving mode is a state where the microcomputer <b>11</b> is shut down, thereby further reducing the power consumption. Specifically, the power saving mode is a state where the clock signal is not supplied from the oscillator circuit <b>17</b> to the main circuit <b>16</b>. Moreover, there are two different power saving modes, i.e., a first power saving mode in which the supply of the clock signal to the timer circuit <b>18</b> is also stopped (in this mode, the oscillation of the oscillator circuit <b>17</b> itself may be shut down), and a second power saving mode in which the clock signal is supplied to the timer circuit <b>18</b>. In the first power saving mode in which the clock signal is not supplied to the timer circuit <b>18</b>, the power consumption can be further reduced. While the microcomputer <b>11</b> can analyze the remote control signal and perform various operations based on the remote control signal in the normal mode, the microcomputer <b>11</b> cannot perform these operations in the power saving mode. Therefore, the microcomputer <b>11</b> is always in the normal mode while it is not on standby (i.e., in the power-ON state), whereas the microcomputer <b>11</b> may be either in the power saving mode or in the normal mode while it is on standby. The presence/absence of the clock signal from the oscillator circuit <b>17</b> is controlled as follows. The supply of the clock signal from the oscillator circuit <b>17</b> to the main circuit <b>16</b> and/or the timer circuit <b>18</b> is stopped by an instruction from the main circuit <b>16</b> (e.g., by opening a switch provided between the oscillator circuit <b>17</b> and the main circuit <b>16</b> and/or the timer circuit <b>18</b>). The supply of the clock signal from the oscillator circuit <b>17</b> to the main circuit <b>16</b> and/or the timer circuit <b>18</b> is started by a first interrupt signal or a second interrupt signal (e.g., by closing a switch provided between the oscillator circuit <b>17</b> and the main circuit <b>16</b> and/or the timer circuit <b>18</b>).

0027The microcomputer <b>11</b> has an interrupt terminal <b>14</b>. The interrupt terminal <b>14</b> is connected to the remote control signal receiving circuit <b>12</b>, and a remote control signal input to the remote control signal receiving circuit <b>12</b> is converted to an electric signal and input to the interrupt terminal <b>14</b>. The signal input to the interrupt terminal <b>14</b> is supplied to the main circuit <b>16</b> as a first interrupt signal, and is also supplied to the main circuit <b>16</b> as a remote control signal. When the first interrupt signal is received while the microcomputer <b>11</b> is staying in the power saving mode, the microcomputer <b>11</b> transitions from the power saving mode to the normal mode. Specifically, when the microcomputer <b>11</b> being in the power saving mode receives the first interrupt signal via the interrupt terminal <b>14</b>, the microcomputer <b>11</b> is interrupted at an edge of the first interrupt signal and transitions to the normal mode.

0028<figref idref="DRAWINGS">FIG. 2A</figref> and <figref idref="DRAWINGS">FIG. 2B</figref> are timing charts illustrating the remote control signal (first interrupt signal) and the operation state of the microcomputer <b>11</b>. In the standby state, the microcomputer <b>11</b> stays in the first power saving mode until the microcomputer <b>11</b> receives a remote control signal (period T<b>1</b>). In the standby state, while a received remote control signal is being analyzed, the microcomputer <b>11</b> periodically repeats the normal mode and the second power saving mode (this operation is herein referred to as an “intermittent operation”) (period T<b>2</b>). Thus, a remote control signal is analyzed while the operation is in the normal mode during the intermittent operation. The microcomputer <b>11</b> analyzes a remote control signal by determining the level (either high or low) of the remote control signal. By setting the period of the intermittent operation to be smaller than the period of the code of the remote control signal (e.g., by setting it to be 250 microseconds), it is possible to accurately analyze the remote control signal even if the remote control signal is analyzed only in the normal mode and it is not analyzed in the second power saving mode. Then, after exiting the standby state (i.e., in the power-ON state), the microcomputer <b>11</b> stays in the normal mode irrespective of whether a remote control signal is being received (period T<b>3</b> of <figref idref="DRAWINGS">FIG. 2B</figref>). In period T<b>3</b> of <figref idref="DRAWINGS">FIG. 2A</figref>, since the remote control signal is a non-power-requesting signal, the device does not exit the standby state, and the microcomputer <b>11</b> stays in the first power saving mode (the details will be described later).

0029The operation of the power saving device <b>10</b> will now be described in detail with reference to <figref idref="DRAWINGS">FIG. 2A</figref>, <figref idref="DRAWINGS">FIG. 2B</figref> and <figref idref="DRAWINGS">FIG. 3</figref>. <figref idref="DRAWINGS">FIG. 3</figref> is a flow chart showing an operation of the power saving device <b>10</b> (interrupt routine). First, referring to <figref idref="DRAWINGS">FIG. 2A</figref>, an operation of the microcomputer <b>11</b> in the standby state (periods T<b>1</b> and T<b>2</b>) will be described. The transition from the normal mode to the power saving mode is made as follows. When the device is in the standby state (YES in S<b>302</b>) and no remote control signal is being received (NO in S<b>303</b> and S<b>307</b>), the microcomputer <b>11</b> shuts down the timer circuit <b>18</b> so that the second interrupt signal is not received from the timer circuit <b>18</b> (S<b>308</b>). Then, the microcomputer <b>11</b> enables an interrupt circuit therein so that the first interrupt signal can be received from the remote control signal receiving circuit <b>12</b> via the interrupt terminal <b>14</b> (S<b>309</b>). Then, the main circuit <b>16</b> instructs the oscillator circuit <b>17</b> to stop the supply of the clock signal to the main circuit <b>16</b> and the timer circuit <b>18</b>, and the microcomputer <b>11</b> thus enters the first power saving mode (S<b>310</b>). As a result, in period T<b>1</b>, the microcomputer <b>11</b> stays in the first power saving mode (S<b>310</b>) until a remote control signal is received by the remote control signal receiving circuit <b>12</b> (i.e., until the first interrupt signal is input to the main circuit <b>16</b> via the interrupt terminal <b>14</b>). This is a state where the clock signal is not supplied to the main circuit <b>16</b> or the timer circuit <b>18</b>, and is a state where the power consumption of the microcomputer <b>11</b> is minimized.

0030The operation in period T<b>2</b>, where a remote control signal is being received, will now be described. The remote control signal receiving circuit <b>12</b> converts a received remote control signal to an electric signal, and passes the signal to the interrupt terminal <b>14</b>. As the first interrupt signal is input to the main circuit <b>16</b> from the remote control signal receiving circuit <b>12</b> via the interrupt terminal <b>14</b>, the microcomputer <b>11</b> transitions from the first power saving mode to the normal mode (time t<b>1</b>). Specifically, the first interrupt signal closes a switch (not shown) between the oscillator circuit <b>17</b> and the main circuit <b>16</b> (and the timer circuit <b>18</b>), whereby the clock signal is supplied from the oscillator circuit <b>17</b>. The presence/absence of the first interrupt signal is determined based on an edge (rising edge or falling edge) of the first interrupt signal. Thereafter, the microcomputer <b>11</b> disables the interrupt circuit therein so that the main circuit <b>16</b> will not receive the first interrupt signal via the interrupt terminal <b>14</b> (S<b>311</b>). Then, the count operation of the timer circuit <b>18</b> is started so as to count a predetermined amount of time (e.g., 250 microseconds) based on the clock signal from the oscillator circuit <b>17</b> (S<b>312</b>). Moreover, the microcomputer <b>11</b> enables the interrupt circuit therein so that the second interrupt signal can be received from the timer circuit <b>18</b> (S<b>312</b>). As will be described later, the timer circuit <b>18</b> gives an interrupt signal to the main circuit <b>16</b> each time the timer circuit <b>18</b> counts 250 microseconds. Then, the microcomputer <b>11</b> sets a flag indicating that a remote control signal is being received (S<b>313</b>).

0031The main circuit <b>16</b> of the microcomputer <b>11</b> analyzes the code of the remote control signal (S<b>301</b>). The code of a remote control signal is typically analyzed by determining the level (either high or low) of the remote control signal. Then, the microcomputer <b>11</b> determines whether or not the device is in the standby state (S<b>302</b>). Since the device is in the standby state (YES in S<b>302</b>) in the illustrated example, the microcomputer <b>11</b> then determines whether or not the remote control signal has been received completely by, for example, checking the number of bits of the received remote control signal (S<b>303</b>). In other words, the microcomputer <b>11</b> determines whether or not the analysis of the remote control signal has been completed. At this point, the remote control signal has not been received completely (NO in S<b>303</b>). Therefore, the microcomputer <b>11</b> determines whether or not the remote control signal is being received based on the flag (S<b>307</b>). Since the flag has been set in S<b>313</b> (YES in S<b>307</b>), the main circuit <b>16</b> instructs the oscillator circuit <b>17</b> to stop only the supply of the clock signal to the main circuit <b>16</b>, whereby the microcomputer <b>11</b> transitions to the second power saving mode at time t<b>2</b> (S<b>314</b>). Thus, while the clock signal is not supplied to the main circuit <b>16</b>, the clock signal is supplied to the timer circuit <b>18</b>. This is done so that the timer circuit <b>18</b> continues the count operation. The power consumption in this mode of operation is lower than that in the normal mode but is slightly larger than that in the first power saving mode of S<b>310</b>. Since the count operation of the timer circuit <b>18</b> is started in S<b>312</b>, the second interrupt signal is input from the timer circuit <b>18</b> to the main circuit <b>16</b> at time t<b>3</b> (250 microseconds after time t<b>1</b>), whereby the microcomputer <b>11</b> transitions from the second power saving mode to the normal mode. Specifically, the second interrupt signal closes a switch (not shown) between the oscillator circuit <b>17</b> and the main circuit <b>16</b>, whereby the clock signal is supplied from the oscillator circuit <b>17</b>.

0032Thus, in the period t<b>1</b>-t<b>2</b>, the microcomputer <b>11</b> is in the normal mode and analyzes the code of the remote control signal, whereas in the period t<b>2</b>-t<b>3</b>, the microcomputer <b>11</b> is in the second power saving mode and shut down, thereby saving the power consumption. The period t<b>1</b>-t<b>2</b> is an amount of time required for the microcomputer <b>11</b> to perform S<b>301</b>, S<b>302</b>, S<b>303</b>, S<b>307</b> and S<b>314</b>, and is 50 microseconds, for example. The shorter this time period is, the shorter a normal mode period is, thus further reducing the average power consumption in period T<b>2</b>.

0033The microcomputer <b>11</b> analyzes the code of the remote control signal at time t<b>3</b> (S<b>301</b>), and it is determined that the device is in the standby state (YES in S<b>302</b>), that the remote control signal has not been received completely (NO in S<b>303</b>), and that the remote control signal is being received (YES in S<b>307</b>), whereby the microcomputer <b>11</b> transitions to the second power saving mode at time t<b>4</b> (S<b>314</b>). Since the count operation of the timer circuit <b>18</b> is started in S<b>312</b>, the second interrupt signal is input to the main circuit <b>16</b> from the timer circuit <b>18</b> at time t<b>5</b> (250 microseconds after time t<b>3</b>), whereby the microcomputer <b>11</b> transitions to the normal mode. Thus, in the period t<b>3</b>-t<b>4</b>, the microcomputer <b>11</b> is in the normal mode and analyzes the remote control code, whereas in the period t<b>4</b>-t<b>5</b>, the microcomputer <b>11</b> is in the second power saving mode and shut down. The operation as described above is repeated until a remote control signal is received completely (i.e., until the determination result in S<b>303</b> is YES), wherein the microcomputer <b>11</b> repeats the normal mode and the second power saving mode with a period of 250 microseconds.

0034The operation after the analysis of the remote control signal (period T<b>3</b>) will now be described. <figref idref="DRAWINGS">FIG. 2A</figref> shows a case where the remote control signal is a non-power-requesting signal, and <figref idref="DRAWINGS">FIG. 2B</figref> is a case where the remote control signal is a power-requesting signal (note that the operation in <figref idref="DRAWINGS">FIG. 2A</figref> is the same as that in <figref idref="DRAWINGS">FIG. 2B</figref> in periods T<b>1</b> and T<b>2</b>). A power-requesting signal as used herein refers to a signal in response to which the main circuit <b>16</b> needs to activate the controlled section <b>15</b> (e.g., “Power-ON/Standby”, “Tray Open/Close” and “Play” of a CD player). In other words, a power-requesting signal is a signal in response to which the device needs to exit the standby state and be turned ON. A non-power-requesting signal as used herein refers to a signal in response to which the main circuit <b>16</b> does not need to activate the controlled section <b>15</b> (e.g., “Stop” and “Skip” of a CD player). In other words, a non-power-requesting signal is a signal in response to which the device does not need to exit the standby state.

0035The case of <figref idref="DRAWINGS">FIG. 2A</figref> will be first described. The microcomputer <b>11</b> analyzes the remote control signal at time tn−1 (S<b>301</b>) and, if it is determined that the remote control signal has been received completely (YES in S<b>303</b>), resets the flag (which has been set in S<b>313</b>) (S<b>304</b>), and it is determined whether or not the remote control signal is a power-requesting signal based on the result of the analysis in S<b>301</b> (S<b>305</b>). Since the remote control signal is a non-power-requesting signal in the illustrated example (NO in S<b>305</b>), the microcomputer <b>11</b> shuts down the count operation of the timer circuit <b>18</b> and disables the interrupt circuit therein so that the second interrupt signal will not be received from the timer circuit <b>18</b> (S<b>308</b>). Then, the microcomputer <b>11</b> enables the interrupt circuit therein so that the first interrupt signal can be received from the remote control signal receiving circuit <b>12</b> via the interrupt terminal <b>14</b> (S<b>309</b>). Then, the microcomputer <b>11</b> transitions to the first power saving mode at time tn (S<b>310</b>). Therefore, in the case of <figref idref="DRAWINGS">FIG. 2A</figref>, the intermittent operation is performed only while a remote control signal is being received, and the microcomputer <b>11</b> transitions back to the first power saving mode after the intermittent operation. Thus, if the remote control signal is a non-power-requesting signal, the device does not exit the standby state and the microcomputer <b>11</b> stays in the first power saving mode.

0036The case of <figref idref="DRAWINGS">FIG. 2B</figref> will now be described. If the remote control signal is determined to be a power-requesting signal based on the result of the analysis in S<b>301</b> (YES in S<b>305</b>), the microcomputer <b>11</b> exits the standby state and is turned ON (S<b>306</b>). Thus, in this case, the microcomputer <b>11</b> stays in the normal mode after time tn−1. Therefore, in the case of <figref idref="DRAWINGS">FIG. 2B</figref>, the intermittent operation is performed only while a remote control signal is being received, and the microcomputer <b>11</b> stays in the normal mode after the intermittent operation. Thus, if the remote control signal is a power-requesting signal, the device transitions from the standby state to the power-ON state, and the microcomputer <b>11</b> stays in the normal mode thereafter.

0037If a remote control signal is received in the power-ON state (where the device is not on standby), it is determined in S<b>302</b> that the microcomputer <b>11</b> is not in the standby state, thereby exiting the interrupt operation.

0038It is determined in S<b>303</b> of <figref idref="DRAWINGS">FIG. 3</figref> that a remote control signal has been received completely even in cases other than when the remote control signal is received normally and completely. For example, when it is determined that a remote control signal is not a valid remote control signal, the remote control signal is discarded, in which case it is determined in S<b>303</b> that a remote control signal has been received completely. Also in this case, it is determined in S<b>305</b> that the remote control signal is a non-power-requesting signal, whereby the microcomputer <b>11</b> transitions to the first power saving mode (S<b>310</b>). Note that a remote control signal being invalid means that the leader code or the custom code of the remote control signal is invalid. A leader code is a code provided for distinguishing a remote control signal of an intended standard from those of different standards or interference signals other than remote control signals. A custom code is a code provided for distinguishing a remote control signal from an intended remote control transmitter from those from other remote control transmitters. Also when only a portion of a remote control signal can be received or when an interference signal contaminates a remote control signal, whereby the code cannot be analyzed properly, the remote control signal is discarded, and it is determined in S<b>303</b> that a remote control signal has been received completely. Again, it is determined in S<b>305</b> that the remote control signal is a non-power-requesting signal, whereby the microcomputer <b>11</b> transitions to the first power saving mode (S<b>310</b>).

0039As described above, the power saving device <b>10</b> of the present embodiment periodically repeats the normal mode and the second power saving mode while a remote control signal is received and analyzed in the standby state, whereby it is possible to reduce the average power consumption of the microcomputer <b>11</b> while receiving a remote control signal.

0040While a preferred embodiment of the present invention has been described above, it is understood that the present invention is not limited thereto.

0041The present invention can suitably be used in electronic devices of various applications where a reduction in the standby power consumption is desired, including TV sets, AV devices such as audio devices, AV receivers and DVD players, and personal computers.